Principate

The Principate (27 BC-284 AD) was the first era of the Roman Empire, lasting from Augustus' proclamation of the empire until the Crisis of the Third Century. It was named for Augustus' ambiguous title princeps ("first citizen") designed to conceal his military dictatorship. The Principate lasted until 284, when the dominate era began.

History
In 27 BC, following the Battle of Actium four years earlier, Octavian (the adoptive son of Julius Caesar) ruled over a united Roman Republic. With Rome being at its strongest since Caesar's death, he proclaimed himself "Augustus" and declared the transition from republic to empire. The Roman Empire took power, although the emperors tried to create the illusion that the Roman republic was still alive. There was still a senate in the empire and the people could still have some role in politics, but the emperors concerted their efforts to hide the fact that they were virtually absolute monarchs. The era ended in 284 with the start of the Crisis of the Third Century, after which the despotic Dominate took power.